You are certainly correct, not a single one of us would have "turned down" an S2k or 350Z if we'd been offered one as an hs grad gift. We just think that they are too fast (and therefore too dangerous) for someone with limited driving experience. To go from a low power front drive car to a high-power rear drive car is a huge change, especially (and I'm guessing here) since you probably have very little experience driving a rear-wheel drive car in the first place.

A safer option would be something like a WRX. Not to dis on your driving skills, but it's almost a certainty that you will wreck the S2k or 350Z within a year. I wrecked my minivan when I was 18. Almost all of my friends destroyed their first car, and none of them even had cars that were fast enough to be dangerous. We basically see it as a waste of a good car, since we're all assuming it will be totalled. I certainly wish you good luck and don't want you to get into an accident, but I'm not holding out a lot of hope.